Two variants of NMR-based conformational analyses of flexible peptides are compared using two examples meeting the formula Tyr-D-Daa-Phe-Daa-NH₂ (Daa=diamino acid): 1 combining D-Dab² (α,γ-diaminobutyryl) with Lys⁴, and 2 -D-Dap² (α,β-diaminopropionyl) with Orn⁴. The ω-amino groups of D-Daa² and Daa⁴ are coupled with C=O into the urea, restraining 1 and 2… (More)

Six hybrid N-ureidoethylamides of octapeptides in which an N-terminal cyclic structure related to enkephalin was elongated by a C-terminal fragment of deltorphin were synthesized on MBHA resin. The synthetic procedure involved deprotection of Boc groups with HCl/dioxane and cleavage of the peptide resin with 45 % TFA in DCM. d-Lys and d-Orn were… (More)

In recent years, a massive effort has been directed towards designing potent and selective antagonists of neurohypophyseal hormones substituted at position 3. Modification of vasopressin at position 3 with 4,4'-biphenylalanine results in pharmacologically inactive analogues. Chemically, this substitution appears to vary only slightly from those previously… (More)